The arrests are part of an investigation into alleged bribery offenses at Izmir's city hall and come after a similar operation in opposition-controlled Istanbul in March when Erdogan's main rival, the city's mayor Ekrem Imamoglu, was removed and imprisoned.
A former mayor of Izmir, Tunc Soyer, and several "high-ranking officials" are among those arrested in the country's third largest city where the opposition has been in power for several years, according to Murat Bakan, vice chairman of the opposition party CHP.
In total, the prosecutor's office has ordered 157 arrests in the city, local media reports.
Bakan calls the arrests "a clear political choice". "These people are in the public eye every day. If they had been called to testify, they would have done so", he writes on X.
The raid took place just hours before the CHP was to hold a demonstration outside the city hall in Istanbul to mark that it has been 100 days since Imamoglu - the party's presidential candidate for 2028 - was removed and imprisoned.
The arrest of Imamoglu and hundreds of other officials in Istanbul triggered a wave of protests that spread across the country and led to mass arrests of demonstrators.
Although the protests have subsided, the CHP has since held election rallies across Turkey, which has strengthened the party's position in opinion polls.
